Three Weeks to Summer Fit

A crash workout is not the best way to get in shape. Eating well and exercising daily over a long period is a much healthier – and easier – approach to getting a body you can live with. But if it's a matter of vanity, not long-term well-being, you can turn your body around fast. "Three weeks may seem last minute," says Ron Mathews, a Hollywood trainer who specializes in high-intensity circuit routines and who designed this 21-day workout for us. "But you just need to maximize caloric output and minimize calorie input while activating as many muscles as possible."

Simple. Grueling. Effective. Here's your plan.

Day 2: Cut Your Calories

Fat reduction won't happen without a disciplined diet, so begin consuming 2,000 calories daily (with about 60g fat and 120g of protein). But don't eat much less – your body will think it's starving and may start storing calories.